Personally I wouldnt bother booking one with the T/O unless it's purely for peace of mind . They usually charge a fortune and most hotels allow you to arrange through recepton on the morning of departure anyway.
They normally tell you to come and check in the morning . We usually have 2 rooms and generally find they allow us to keep one of them at a small charge. Dont pay anything anymore at the hilton as we have a hilton honors card . At the worst they will make a room available to you or allow you to use the spa or something to change and have a shower.
Definately email any requests to the Tropicana direct nearer your departure time . Usually 10-14 days before because they wont have details of your booking from the T/Ops before then . You can't always rely on flight times this early in advance anyway and that could always change . I wouldnt worry too much yet .